Tolerance compensating electrode support structure and method of manufacturing same



Jan. 24, 1967 T. P. CURTIS ETAL TOLERANCE COMPENSATING ELECTRODE SUPPORT STRUCTURE AND METHOD OF MANUFACTURING SAME Original Filed Aug. 20, 1962 2 Sheets-Sheet l FIG.I.

INVENTORS TRUMAN P. CURTIS, JAMES R.M.; VAUGHAN,

BY THEIR ATTORNEY.

Jan. 24, 1967 T. P. CURTIS ETAL R 3,300,673

TOLERANCE COMPENSATING ELECTRODE SUPPORT STRUCTURE AND METHOD OF MANUFACTURING SAME Original Filed Aug. 20, 1962 2 Sheets-Sheet 2 INVENTORSI TRUMAN P. CURTIS, JAMES R. M. VAUGHAN BY/V% HEIR ATTORN United States Patent TOLERANCE COMPENSATING ELECTRODE SUP- PORT STRUCTURE AND NETHOD 0F MANU- FACEUG SAME Truman P. Curtis, Schenectady, and James R. M. Vaughan, Scotia, N.Y., assignors to General Electric Company, a corporation of New York Continuation of application Ser. No. 217,943, Aug. 20, 1962. This application May 16, 1966, Ser. No. 550,564

13 Claims. (Ql. 313--153) This is a continuation of Serial No. 217,943, filed August 20, 1962, now abandoned.

Our invention relates to electric discharge devices and pertains more particularly to a new and improved means and method for mounting a cathode coaxially in a magnetron.

In the manufacture of a magnetron, the usual manner of mounting a cathode therein generally consists of fixturing the cathode in accurate spaced relationship to the anode and then elfecting either a glass seal or a brazed joint between a stem on the cathode and appropriate support structure fixedly attached to the 'anode. When a glass seal is employed the plastic characteristics of the sealing glass allow it to flow and compensate for any misalignment of the sealing surfaces. Thus, in this type of structure a substantial degree of misalignment between the cathode stem and the support is tolerable. However, in the manufacture of many magnetron devices it is desirable, and sometimes necessary, to avoid the use of glass and to use a brazed joint of the type referenced above. Such brazed joint generally involves the use of ceramic-to-metal seals and heretofore it has been found necessary to provide close parts tolerances in order to maintain a relatively tight fit between the cathode stem and support structure for the purpose of insuring a satisfactory ceramic-to-metal joint between these elements. long stem was required to compensate for tolerances in the individual concentric elements and subassemblies joined to comprise the overall assembly. That is, the long cathode stem permitted small angular misalignment of the cathode and anode thereby to compensate for mechanical tolerances of the separate elements comprising the overall assembly While maintaining a close fit between the sealing surfaces in order to enable the making of a reliable joint therebetween.

As indicated above, in the manufacture of some magnetron devices it is desirable or necessary to avoid the use of glass. In other magnetron devices it is desirable or necessary, due to space considerations or other design factors, to provide a short-stemmed cathode mount. This necessitates the provision of mounting means and methods different from those described above but which must be effective for providing the required accurate coaxial alignment of the cathode in the anode. Additionally, it is desirable to provide means and methods which avoid the necessity of manufacturing device elements and subassemblies with close tolerances to insure accurate alignment of the cathode and anode in an assembled device.

Accordingly, a primary object of our invention is to provide a new and improved means and method for accurately mounting coaxial electrodes.

Another object of our invention is to provide a new and improved means and method for accurately mounting a cathode coaxially in an anode bore.

Another object of our invention is to provide a new and improved means and method for avoiding the necessity of providing closely-toleranced and tightly-fitted parts in the mounting of axially aligned coaxial electrodes.

Aditionally, the use of a substantially Patented Jan. 24, 1967 Another object of our invention is to provide a new and improved means and method for mounting magnetron cathode and anode elements in accurate aligned coaxial relation without relying on long-stemmed members and thus enabling a more compact device construction.

Another object of our invention is to provide a new and improved means and method for coaxially accurately mounting electrode elements in a manner which simplifies the fabrication of the individual elements used and which enables substantial reductions in cost and elfort involved.

Further objects and advantages of our invention will become apparent as the following description proceeds and the features of novelty which characterize our invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

In carrying out the objects of our invention there is provided a magnetron device including an envelope section having an anode structure rigidly mounted therein. The anode structure comprises a plurality of radially extending anode segments defining a central bore therein. The envelope section also supports a member extending transverse the axis of the anode bore and adapted for supporting a cathode assembly. This member can additionally serve as an internal magnetic pole piece. It can also serve as an end Wall section of the envelope, if desired. The device further includes a cathode assembly comprising a generally tubular emitter extending in the anode bore and a tubular axial extension. The extension protrudes through an aperture in the transverse support member and a tubular ceramic insulator mounted on the side of the support member opposite the anode structure. A metal sealing ring joins one end of the ceramic insulator to the support member and another metal sealing ring is bonded to the opposite, or outer, end of the insulator. The last-mentioned sealing ring has brazed thereto a washer-like metal sealing ring having the cathode extension protruding therethrough. This washer-like member is provided with a recessed upper surface which contains a quantity of metal bonding material which joins the washer-like member to the outer surface of the cathode extension and fills any space therebetween. In the manufacture of this arrangement, and according to the method aspect of our invention, the anode structure and envelope are pre-assembled to have the anode structure fixedly mounted relative to the transverse support member and to have the various sealing rings, except the washer-like member, and ceramic insulator mounted on the support member. Then the cathode is accurately aligned coaxially and angularly relative to the anode bore and anode segments, respectively, by a suitable fixture adapted for holding the cathode in the desired aligned position fixedly relative to the anode. Following this, the washer-like sealing member is positioned on the cathode extension with a free fit. Then metal bonds are effected between the washer-like member and cathode stem and between the washer-like member and the sealing ring on the outer end of the insulator and the washer-like member compensates for any accumulation of parts tolerances. Additionally, the washerlike member is advantageously formed of a material which is readily heated by RE induction heating to effect desired flow of solder material positioned between it and adjacent elements to effect the just-mentioned bonds. If the transverse support member serves also as a wall section of the envelope the mentioned bonds and seals must be hermetic; otherwise they need only be mechanically strong.

For a better understanding of my invention reference may be had to the accompanying drawing in which:

FIGURE 1 is a side sectional view of a preferred embodiment of the invention wherein the misalignment of elements is shown exaggeratedly for the purpose of better illustrating the invention;

FIGURE 2 is a fragmentary, exploded perspective view of the preferred embodiment of the invention; and

FIGURES 3 and 4 are fragmentary, sectional views illustrating the several element-s incorporated in the preferred embodiment and the steps involved in the manufacture of the completed assembly.

Referring now to the drawing, there is shown in FIG- URE 1 a magnetron device including an envelope 1 comprising a cylindrical metal wall section 2 having sealed across the opposite ends thereof upper and lower end wall sections 3 and 4, respectively. Mounted fixedly in the envelope are upper and lower transverse members and 6, respectively. The members 5 and 6 are adapted for serving as internal magnetic pole pieces. Additionally, the upper member 5 serves effectively as a cathode assembly support in a manner to be described in detail hereinafter. Further, if desired, the members 5 and 6 could serve also as end wall sections, in which case the end wall sections 3 and 4 could be dispensed with.

Contained in the envelope 2 and positioned in axial spaced relation between the members 5 and 6 is an anode assembly 7. The anode assembly 7 includes a plurality of circumferentially spaced radially extending anode segments or vanes 8 defining a central cylindrical bore 9. Provided for being mounted coaxially in the bore 2 is a cathode assembly generally designated 10. The cathode assembly 10 can advantageously be an indirectly heated cathode comprising a tubular emissive section 11 containing a heating element (not shown). Additionally, the cathode assembly includes a non-emissive axial extension or stem 12 having a laterally exposed sealing surface 13 located at the outer end thereof. As seen in the drawing, the stem 12 is short relative to the emissive section 11. Also, the emissive section 11 can have a corrugated outer surface, or can be formed to include radially extending and circumferentially spaced protrusions. The corrugations on the emitter are adapted for corresponding in number to the anode vanes 8 and for being disposed in predetermined angular relation to the corresponding vanes. The corrugated cathode and the predetermined angular relation between cathode corrugations and anode vanes do not constitute part of the present invention but are disclosed and claimed in copending US. application S.N. 105,983 of J. E. Staats filed April 27, 1961 and assigned to the same assignee as the present invention. However, the present invention contemplates means and a method which, in addition to providing for accurate aligned relation of the cathode in the anode bore, is effective for facilitating assembly of the device to obtain the mentioned desired angular relation of cathode corrugations and anode vanes.

The cathode assembly 10 is mounted on and supported from the upper internal pole piece 5 which includes a central aperture 14 having the cathode extension 12 protruding therethrough. Bonded to the member 5 on the side opposite the anode structure is a sheet-metal sealing ring 15 which is provided with outer and inner flanges 15a and 15b, respectively. The outer flange 15a is butt-sealed to the membed 5 about the aperture 14. The inner flange 15b is butt-sealed to one end of a tubular ceramic insulator or sleeve 16 which is of greater inside diameter and substantially shorter axial length than the cathode extension 12. In this sealing arrangement the pole piece 5 and the insulator 16 are thermally mismatched and the ring 15, which more closely matches the thermal expansion properties of the insulator, is provided to insure a satisfactory joint. Butt-sealed to the other end of the ceramic insulator 16 is a flanged sheetmetal collar-like sealing ring 17 having a generally cylindrical coaxial extension 17a. The bonds between the sealing rings 15 and 17 and the insulator 16 can be formed by any of the well-known ceramic-to-metal sealing techniques.

The cylindrical section 17a of the sealing ring 17 has an inner diameter appreciably greater than the outer diameter of the cathode extension 12, which protrudes therethrough without touching. However due to accumulations of parts tolerances, the cathode extension 12 will not generally be perfectly coaxial with the cylindrical portion 17a, when the cathode surface 11 is held accurately coaxial with the anode bore 9. The gap between the sealing surface 13 on the cathode extension 12 and the cylindrical portion 17a of sealing ring 17 is bridged by a relatively massive washer-like sealing ring or member 20. The member 20 is made to fit freely on the surface 13 of cathode extension 12, by which is meant that it can slide easily up and down, and can be tilted through small angles, thus enabling member 20 to lie flat on the top of ring 17a even though extension 12 may be slightly tilted with respect to ring 17a. Further, the outer diameter of the sealing member 20 is appreciably greater than the outer diameter of ring 17a so that member 20 overlaps ring 17a at all points of the circumference even though extension 12 may be eccentric with respect to ring 17a. The member 20 is bonded both to the ring 17a and to the sealing surface 13 of cathode extension 12.

The sealing member 29 is formed of a metal which is both readily heated by RE. induction heating, such for example as iron or fernico, and is readily wettable by a solder material such as silver solder. Additionally, the upper surface of the member 20 is countersunk or formed with a frusto-conical depression or recess 20a shown in FIGURE 2 and which is disposed about the opening through the ring and is adapted for providing an annular recess about the cathode extension when the cathode extension is positioned in the ring in the manner illustrated in FIGURE 3. As also illustrated in FIGURE 3, the annular recess 20a is adapted for receiving a quantity of solder material which can be in the form of a solder ring 29 illustrated in FIGURES 2-4. Additionally, the thinning of member 20 on its inner edge allows it to swivel on stem 12 more easily, thereby facilitating the correction of errors of tilt in a manner to be discussed in detail hereinafter in connection with the description of the method of manufacturing aspect of our invention. Further, the depression in the member 20 is effective for presenting a substantial sealing surface on the ring to which the solder can adhere. Still further, the sealing member 20 is formed of substantially thicker stock than that used in forming the sealing rings 15 and 17. This, together with its flat washer-like construction, renders it relatively rugged whereby it is adapted for afifording substantial rigidity to the cathode mount and serving as a cathode contact to which a lead wire 22 can be suitably conductively connected. The lead wire 22 connects the cathode to a cathode terminal 23 suitably sealed in the upper end wall section 3 in insulated relation thereto. Similarly sealed in the wall section 3 is a heater terminal 24 which is connected by a lead wire 25 to one leg of the heater (not shown) contained in the emitter 11. The other leg of the heater is connected to the cathode assembly whereby cathode terminal '23 is adapted for serving as a heater terminal also.

In the above-described device no less than nine separate elements must be traversed in going from the emitter 11 to the anode bore 9. This fact and the concentricity tolerances of the various elements must be considered in providing an arrangement which will be effective in mounting the cathode accurately coaxially in the anode bore. More specifically, the device comprises a number of concentric elements including, for example, the elements designated 2, 5, 7, 11, 12, 15, 16, 17, 20. In the manufacture of these elements each is ordinarily fabricated with its own concentricity tolerances. Thus, if in assembling the overall device, one were to depend on mechanical fit of the several elements alone to obtain accurate coaxial alignment and concentricity of cathode and anode, the final concentricity tolerance of the cathode in the anode would be anything up to 9 times the average part tolerance, with an R.M.S. (root-mean-square) value three times the average part tolerance. This would require the individual parts to be made an order of magnitude more precise than the final concentricity required, which would be economically, if not practically, unacceptable. As mentioned above, this problem has heretofore been solved to some extent by employing a long cathode stem which allowed one to compensate for eccentricity of parts by introducing a slight misalignment of the cathode in the anode to compensate for mechanical tolerances of the separate assemblies while maintaining a close fit between the sealing surfaces in order to effect reliable joints.

The present invention obviates the need for long stems and thus serves to enable shortening of the device length. Additionally, it allows all part tolerances to accumulate up to a certain point, without holding each to any very small value, and then compensates for all of them at once by taking them up in what can be a variable overhang rat the washer-like sealing ring or part 29. Further, it not only obviates the need for introducing a tilt, or misalignment, of parts, but takes up and compensates any existing errors of tilt as well as of concentricity.

In assembling the described structure, and according to the method aspect of our invention, we first assemble separately the cathode assembly and the anode assembly. Additionally, we separately mount the anode assembly in the envelope cylinder 2, secure the upper pole piece in place and bond the sealing rings and 17 and the ceramic insulator 16 all in place in the stacked arrangement shown in the drawing. As shown exaggeratedly in FIGURE 1, the various parts need not be accurately formed or positioned. For example, the cathode stem 12 may be tilted with respect to the emitter 11, the sealing ring 15 may :be distorted, the top edge of the sealing member 17 may be eccentric and tilted and the transverse end surfaces of the insulator 16 may be non-parallel and non-perpendicular with respect to the longitudinal axis thereof.

Subsequently, We mount the preassembled cathode assembly in a fixture 26 which is best seen in FIGURES 2 and 3. The lower end pole piece 6 has not as yet been secured in place and the fixture 26 is placed in position through the open lower end of the cylinder 2. The fixture 26 includes indexing elements 27 which are positioned in grooves in the corrugated cathode member 11 and cooperate with the anode structure 7 to hold the cathode fixedly and accurately coaxially aligned in the anode bore, with the cathode corrugations each in predetermined angular relation to corresponding anode segments and with the cathode extension or stem 12 protruding through the sealing ring 17 on the outer end of the ceramic insulator 16.

Then a ring of solder or brazing material 23 is positioned on the rim of the sealing ring 17 after which the washer-like sealing member is slid or positioned over the protruding end of the cathode extension and sealed on the solder ring 28. As mentioned above, the thinning of member 20 at its inner edge allows it to swivel on the cathode stem more easily. This allows the member 20 to accommodate a tilted stern more readily and allows the member to rest flatly on the end of the member 17. It will be appreciated that if the member 2t) had a cylindrical inner surface it would, unless its inner diameter were substantially greater than the outer diameter of the stern, be prevented :by a tilted stem from resting flatly on the end of the member 17, in which case a strong bond therebetween might not be obtained.

After the member 20 is positioned in the described manner a ring of solder material 29 is positioned over the cathode stem and in the frusto-conical recess or countersunk surface 20a of the sealing ring 20 in the manner illustrated in FIGURE 3. Then, and as shown in FIG- URE 4, the member 20 is heated by RF. induction heating as by means of an induction heating coil 30 to a temperature effective for heating the solder material 2-8 and 29 and causing it to flow to bond the member 219 to the rim of the member 17 and the member 20 to the cathode extension sealing surface 13. It will be understood that solder means other than the ring 28 can be employed in effecting the bond between the members 17 and 29. For example, the opposing surfaces of these elements could be plated, one with silver and the other with copper to form, when heated, a copper-silver eutectic bond at the junction of the parts. Alternatively, reliance may be placed on capillary attraction to draw sufiicient molten braze from the solder ring 29 to complete the joint between the member 17 and 20.

As best seen in FIGURE 1, when the bonds between the sealing member 20 and the member 17 and the cathode stem 12 have both been effected the cathode and aonde bore are accurately coaxially aligned and any misalignments or tilts of the cathode stem or other parts relative to the anode bore axis will all be compensated for by the overhang of the member 20. That is, the member 29 is free to assume and be bonded to the member 17 in a position in which it will accommodate the tilted cathode extension and compensate for any misalignment of parts. Thus, where a great deal of misalignment is present the member 20 can be sealed to the member 17 in a substantial overhanging position such as that illustrated exaggeratedly in FIGURE 1 and in which position it will effectively compensate for the misalignment and rigidly hold the cathode assembly in the position in which the emitter 11 is coaxially accurately aligned in the anode bore 9.

Additionally, according to the present invention the frusto-conical configuration of the inner surface 20a of the sealing member 2%) provides an increased sealing area to which the solder can adhere whereby the strength of the seal is enhanced. Furthermore, the relative thickness of the member 20 provided to afford ready RF. induction heating serves also in providing a rugged seal in the mounting of the cathode, thereby to maintain the desired coaxial alignment provided by the fixture 26 after the seal is effected and the fixture is removed. Still further, the relatively short length of the cathode extension and sealing arrangement including the short insulator 16 serve both to decrease the axial length of the device and to provide a relatively small bending moment at the seal between the cathode stem and sealing ring. This small bending moment serves to insure against failure of the several seals in the structure whereby the cathode is mounted.

It is to be understood from the foregoing that while the present invention is particularly effective for mounting a cathode coaxially in an anode structure the invention is equally applicable to the mounting of any coaxially arranged electrode elements in accurately aligned spaced insulated relation in an electric discharge device envelope. Also, and as brought out above the transverse support member 5 can serve also as an end wall of the envelope structure in which case it will be necessary that the various discussed seals and bonds be hermetic, or vacuum tight, in addition to being mechanically strong.

While we have shown and described a specific embodiment of our invention, we do not desire our invention to tbe limited to the particular forms shown and described, and we intend by the appended claims to cover all modifications within the spirit and scope of our invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. An electric discharge device comprising an envelope, a first electrode mounted fixedly in said envelope and including a central bore, a transverse member mounted fixedly relative to said first electrode, an insulating support comprising a short cylindrical ceramic insulator and a short metal collar sealed to one end thereof, said insulator being sealed at the other end to said transverse member, the axis of said insulating support being subject to misalignment with the axis of said bore due to accumulations of manufacturing tolerances of said parts, a second electrode in accurate spaced coaxial relation to said bore and including a short tubular axial extension protruding in spaced relation through said insulating support, said tubular axial extension being subject to misalignment with the axis of said second electrode due to accumulations of manufacturing tolerances of said parts, the nominal gap between said tubular extension and said collar being greater than the maximum accumulations of said tolerances and a washer-like member closely fitted about said extensions bridging said gap and sealed to both said collar and said tubular extension, whereby all of said accumulations of tolerances are taken up and nullified.

2. An electric dis-charge device according to claim 1, wherein said transverse member and insulator are thermally mismatched and a metal sealing ring having thermal expansion properties more closely matching those of said insulator is interposed and bonded between said transverse member and insulator.

3. An electric discharge device comprising an envelope, a first electrode mounted fixedly in said envelope and including a central bore, a second electrode coaxially positioned in said bore and including a tubular axial extension of minimum length protruding in spaced relation through an aperture in a transverse support member mounlted fixedly relative to said first electrode, and means mounting said second electrode rigidly in said coaxial position comprising an insulative sleeve having one end joined to said support member about said aperture, a metal collar joined to the other end of said insulative sleeve, with said axial extension of said second electrode protruding in spaced relation through said insulative sleeve and said metal collar, and a washer-like metal member surrounding said axial extension and spanning the gap between said extension and said collar, said washer-like member having a tapered inner surface defining an aperture adapted for receiving said axial extension in angular relationship, said washer-like member being further characterized by overlapping the end of said collar to close said gap while at the same time being eccentric with said collar and being joined by a metal-to-metal bond to both said collar and said axial extension of said second electrode.

4. An electric discharge device according to claim 3, wherein the washer-like member is provided with an inner edge of reduced thickness, whereby said washerlike member can pivot slightly about the second electrode extension during assembly for enabling said washer-like member to lie fiat on the metal collar despite any small misalignment between said collar and said axial extension.

5. An electric discharge device according to claim 3, wherein said washer-like member is formed of a material readily heatable by RP. induction heating, whereby the making of said bonds between said member and said collar and said axial extension of said second electrode can be facilitated.

6. A magnetron comprising an envelope including a tubular wall section, an anode structure fixedly mounted in said tubular section and including a plurality of radially extending segments defining a central bore, a pair of pole pieces secured transversely in said tubular wall section in spaced relation to said anode structure, a cathode including a cylindrical emissive section positioned coaxially in said bore, and a short coaxial tubular extension protruding in spaced relation through an aperture in one of said pole pieces, and means mounting said cathode rigidly in said coaxial position and in insulated relation to said envelope and anode structure comprising a short insulative sleeve joined at one end to said pole piece about said aperture, a short metal collar joined to the other end of said insulative sleeve, with said cathode extension protruding in spaced relation through said insulative sleeve and said metal collar, and a washer-like metal member having a reduced inner and lower edge adjacent said extension and defining an annular recess therewith, said Washer-like metal member surrounding said cathode extension and spanning the gap between said cathode extension and said metal collar, a bonding metal in said defined recess to provide a metal-to-metal bond to both said metal collar and said cathode extension.

7. A magnetron according to claim 6, wherein said insulative sleeve is joined to said pole piece through an intermediate metal annulus effective for accommodating any thermal expansion mismatch between said sleeve and said pole piece.

8. The method of manufacturing an electric discharge device containing a pair of coaxially accurately aligned electrode elements and wherein the sum of the manufacturing tolerances of the parts thereof may be greater than the desired concentricity tolerance of said pair of electrode elements, comprising the steps of fabricating separately an assembly including an envelope section having fixedly mounted therein the outer electrode element and a transversely extending inner electrode support member having an aperture therein aligned with the opening in said outer electrode element, bonding an annular insulator having a collar-like metal sealing ring on the outer end thereof to said support member coaxial with said aperture therein, fixedly holding the inner electrode element in coaxial alignment in said outer electrode element and with an axial extension on said second element protruding through said insulator and sealing ring thereon, positioning on the protruding extension of said second element a free fitting washer-like metal sealing member and eflFecting bonds between said free fitting member and both said extension and said collar-like ring on said insulator, whereby said free fitting member compensates for any accumulation of parts tolerances.

9. The method according to claim 8, wherein said free fitting sealing member is formed of a material adapted for being readily heated by RF. induction heating, brazing material is provided between the surfaces to be bonded and both bonds are simultaneously effected by inductively heating said free fitting member.

10. The method of manufacturing an electric discharge device containing a pair of coaxially accurately aligned electrode elements and wherein the sum of the manufacturing tolerances of the parts thereof may be greater than the desired concentricity tolerance of said pair of electrode elements, comprising the steps of fabricating separately, an assembly including an envelope section having fixedly mounted therein the outer electrode element and a transversely extending inner electrode support member having an aperture therein aligned with the opening in said outer electrode element, bonding an annular insulator having a collar-like metal sealing ring on the outer end thereof to said support member coaxial with said aperture therein, fixedly holding the inner electrode element in coaxial alignment in said outer electrode element and With an axial extension on said outer electrode element protruding through said collar-like sealing ring on said insulator, positioning on the protruding extension of said second element a Washer-like sealing member having an inner rim of reduced thickness relative to the outer rim thereof to enable said member to be freely fitted and to swivel readily on said extension and also to afford a depression for receiving a quantity of brazing material for flowing when heated to seal said member to said extension, providing brazing material in said depression and between said washer-like member and said collar-like ring on said insulator and heating said washer-like member to cause said brazing material to flow and simultaneously effect bonds between said washer-like member and said extension and ring on said insulator, whereby said washerlike member compensates for any accumulation of parts tolerances.

11. The method of manufacturing an electric discharge device containing a first electrode having a central bore and a second electrode accurately coaxially positioned in said bore, comprising the steps of fabricating separately an assembly including a tubular envelope section having rigidly mounted therein said first electrode and a transverse second electrode support member having an aperture therein coaxially aligned With said bore in said first electrode, bonding to said support member a tubular insulator coaxial with said aperture therein and having a metal sealing ring on the outer end thereof fixedly holding said second electrode from the open end of said tubular envelope section in accurate coaxial alignment in said first electrode bore and with an axial extension on said second electrode protruding through said sealing ring on said insulatorypositioning over said axial extension and resting on said insulator, a countersunk washer-like sealing member formed of a material adapted for being readily weted by a brazing material and readily heated by an RF. induction heating, providing brazing material in the countersunk portion of said washer-like member and about said axial extension on said second electrode and between said washer-like member and said ring on said insulator, inductively heating said Washerlike member to heat said brazing material for causing same to flow to effectively bond said washer-like member to said electrode extension and to said ring on said insulator, whereby said washer-like member is effective for compensating for any misalignments in the assembly of the aforesaid elements.

12. The method of manufacturing an electric discharge device according to claim 8, wherein the electrodes are held in a desired angular relation as well as in spaced coaxial relation during the bonding operation.

13. An electric discharge device comprising an envelope, a first electrode mounted fixedly in said envelope and including a central bore, a transverse member mounted fixedly relative to said first electrode, an insulating support comprising a short cylindrical ceramic insulator and a short metal collar sealed to one end thereof, said insulator being sealed at the other end to said transverse member, the axis of said insulating support being subject to misalignment with the axis of said bore due to accumulations of manufacturing tolerances of said parts, a second electrode in accurate spaced coaxial relation to said bore and including a short tubular axial extension protruding in spaced relation through said insulating support, said tubular axial extension being subject to misalignment with the axis of said second electrode due to accumulations of manufacturing tolerances of said parts, the nominal gap between said tubular extension and said collar being greater than the maximum accumulations of said tolerances and a washer-like member closely fitted about said extension bridging said gap and sealed vacuum tight to both said collar and said tubular extension, whereby all of said accumulations of tolerances are taken up and nullified.

References Cited by the Examiner UNITED STATES PATENTS Re. 25,420 7/1963 Vaughn et al 3l5-39.67

JAMES W. LAWRENCE, Primary Examiner.

P. C. DEMEO, Assistant Examiner. 

1. AN ELECTRIC DISCHARGE DEVICE COMPRISING AN ENVELOPE, A FIRST ELECTRODE MOUNTED FIXEDLY IN SAID ENVELOPE AND INCLUDING A CENTRAL BORE, A TRANSVERSE MEMBER MOUNTED FIXEDLY RELATIVE TO SAID FIRST ELECTRODE, AN INSULATING SUPPORT COMPRISING A SHORT CYLINDRICAL CERAMIC INSULATOR AND A SHORT METAL COLLAR SEALED TO ONE END THEREOF, SAID INSULATOR BEING SEALED AT THE OTHER END TO SAID TRANSVERSE MEMBER, THE AXIS OF SAID INSULATING SUPPORT BEING SUBJECT TO MISALIGNMENT WITH THE AXIS OF SAID BORE DUE TO ACCUMULATIONS OF MANUFACTURING TOLERANCES OF SAID PARTS, A SECOND ELECTRODE IN ACCURATE SPACED COAXIAL RELATION TO SAID BORE AND INCLUDING A SHORT TUBULAR AXIAL EXTENSION PROTRUDING IN SPACED RELATION THROUGH SAID INSULATING SUPPORT, SAID TUBULAR AXIAL EXTENSION BEING SUBJECT TO MISALIGNMENT WITH THE AXIS OF SAID SECOND ELECTRODE DUE TO ACCUMULATIONS OF MANUFACTURING TOLERANCES OF SAID PARTS, THE NOMINAL GAP BETWEEN SAID TUBULAR EXTENSION AND SAID COLLAR BEING GREATER THAN THE MAXIMUM ACCUMULATIONS OF SAID TOLERANCES AND A WASHER-LIKE MEMBER CLOSELY FITTED ABOUT SAID EXTENSIONS BRIDGING SAID GAP AND SEALED TO BOTH SAID COLLAR AND SAID TUBULAR EXTENSION, WHEREBY ALL OF SAID ACCUMULATIONS OF TOLERANCES ARE TAKEN UP AND NULLIFIED. 